Reverse Engineering My Coway Air Purifier to Ditch the Cloud

The Coway Airmega IconS is a Wi-Fi air purifier whose owner wants to control through an Apple Home “Good Night” scene, turning up its fan for white noise as the lights switch off. The existing Home Assistant integration enables this by polling Coway’s IoCare cloud and sending commands through it, but the service has repeatedly failed because of outages, account bans, app changes, and website changes that broke the integration. Since the purifier is discontinued and the cloud may not last, the goal is to find a way to control it locally instead.

The investigation uses a Raspberry Pi as an isolated Wi-Fi access point, with traffic redirected to mitmproxy so the purifier’s communications can be inspected. The Pi connects to the home network through a laptop because its Wi-Fi signal is too weak to reach the purifier from the router. A recently exposed weakness in an internet certificate authority’s keys offered a possible way to intercept encrypted traffic, provided the purifier is unpatched and does not pin Coway’s certificate. After the purifier’s setup fails on the test network, the proxy nevertheless records an HTTP request for an Amazon root certificate. That trace indicates the device connected to Wi-Fi and began communicating, but the failed setup leaves open how it validates certificates and how its cloud protocol might be replaced.